Defects in HgCdTe grown by molecular beam epitaxy on GaAs substrates

Abstract

The Hall effect and photoluminescence measurements combined with annealing and/or ion milling were used to study the electrical and optical properties of HgCdTe films grown by molecular-beam epitaxy on GaAs substrates with ZnTe and CdTe buffer layers. Unintentional donor doping, likely from the substrate, which resulted in residual donor concentration of the order of 1015 cm−3, was observed in the films. Also, acceptor states, possibly related to structural defects, were observed.

Photoluminescence of HgCdTe nanostructures grown by molecular beam epitaxy on GaAs

“…Such acceptor levels are distinct from shallow va− cancy−related acceptor levels with the energy of~15 meV (see Fig. 1), and were earlier attributed to structural defects specific to HgCdTe grown on GaAs [16]. The FWHM of the single−band PL spectra varied from 18 to 33 meV and did not depend on the alloy composition in the well, thus being deter− mined solely by the degree of alloy disorder in each individ− ual sample.…”

“…Figure 2 shows the PL spectra of as−grown structures #2, #7, #8, #9 and #11 recorded at T = 84 K. As is seen, all the spectra comprised a single PL line with a Gaussian−like shape. Acceptor states found in some MBE−grown HgCdTe films [14][15][16] in general were not typical of the studied nanostructures. Still, in the PL spectra of some structures (e.g., #4, not shown in the graph), an acceptor−related PL band was observed with the energy of the acceptor level of 27 to 33 meV.…”

“…The effect of this disorder on the emissive properties of HgCdTe remained unclear. Also, recently it was shown that defects specific to hetero− −epitaxial HgCdTe grown on a particular substrate affected the optical properties of the epitaxial films [16,17]. Thus, a deeper study of the photoluminescence (PL) of HgCdTe nanostructures grown by MBE on 'alternative' substrates became topical.…”

Background donor concentration in HgCdTe

“…Figure 5 shows more relaxation curves for MBE MCT/GaAs. In particular, shown is post−IM relax− ation in non−annealed (even numbers) and annealed into p−type (odd numbers) films with x = 0.22 (21,22), and with x = 0.30 (23,24) grown in Novosibirsk, and in a p−type MBE film with x = 0.22 and p 77 = 1.3 × 10 16 cm -3 grown in China (25). Note that the value of n 77 (i) after the milling appeared to depend on x (which contrasted these films to MCT/Si, see below).…”

“…MBE currently is the most widely used method of growing MCT for third−generation infrared photodetectors, and MBE−grown material is, perhaps, the one studied most ex− tensively with the use of IM [13,23]. BDC was studied for the material grown on (310)Si and GaAs substrates with CdTe/ZnTe buffer layers, or CdZnTe substrates at A.V.…”